Pant-type absorbent articles commonly include a pant-shaped chassis structure and an absorbent core component integrated with the chassis. A major objective when designing pant articles is to make them resemble ordinary underwear as closely as possible. Hence, absorbent articles such as pant diapers, sanitary pants and incontinence pants are designed to fit comfortably and snugly about the wearer. It is also desirable that the articles are capable of being pulled up and down over the hips of the wearer in the manner of a pair of underpants to allow the wearer or caregiver to easily remove a soiled article and to replace it with a new clean article. For these reasons, the article chassis is usually made of a material that is elastically stretchable, at least around the waist and in the areas intended to be applied over the wearer's hips.
Traditionally, the chassis of pant-type absorbent articles have been made from layers of non-elastic thermoplastic nonwoven material having elastic elements such as threads or bands arranged between the layers to elasticise selected portions of the chassis. In these articles, the fibres and bonds of the nonwoven webs remain unbroken during the production of the chassis structure and can be used to form strong and yet openable welds and seams between the chassis parts. However, in order to meet the demand for more underwear-like pant-type articles, the traditional elastification by means of elastic elements has been replaced by elastic nonwoven/film laminates.
One example of an elastic laminate for use in pant-type absorbent articles is disclosed in WO 03/041988. The laminate is composed of an elastic film applied between two nonwoven layers. During production of the elastic laminate, the nonwoven layers have been bonded to the film after which the laminate has been subjected to activation treatment involving incremental stretching of the laminate that causes bonds and fibres in the nonwoven webs to break. As a result, the elasticity of the activated laminate is largely the same as the elasticity of the elastic film. A problem with activated nonwoven/film laminates of this type is that welded seams formed in the mechanically weakened materials have poor tensile strength. This means that there is a risk that the seams will break prematurely when the pant-type article is put on a wearer or when it is being worn.
Other examples of elastic laminates used in the construction of pant-type articles are disclosed in WO 2005/122984 and WO 2005/122985. The materials in these applications differ from that disclosed in WO 03/041988 in that the bonds and fibres of at least one nonwoven layer in the elastic laminate have not been completely broken. Instead, the layer retains some residual strength. PCT applications WO 2005/122984 and WO 2005/122985 describe laminates in which elasticity has been combined with softness and resistance to puncture of the laminates. However, welded side seams in pant-type articles comprising such laminates still show low tensile strength when compared to the weld seams of traditional pants made of nonwoven layers that have been elasticised by means of elastic threads or bands.
The pant-type absorbent articles are usually formed with seams or joins at the sides of the chassis structure to connect the article's front portion to the rear portion and to form a pant having a waist opening and leg openings. Normally, the side joins are arranged so that they will be placed at the user's hips during use of the absorbent pants, but it is also known to arrange side joins more to the front of the article.
The side-seams are preferably made such that they will provide sufficient integrity to the chassis while it is being put on and while it is being worn. This means that the side-seams should withstand the tensile stress arising when the pant-type article is pulled up over the wearer's hips and also any stress that may occur at the side seams as a result of the wearer's movements during use of the article. However, it has proven to be a great advantage if the side-seams can be broken apart in a controlled manner after use of the article so that a soiled article can be easily removed from the user without having to be pulled down along the legs. Openable side-seams are most readily formed by welding techniques such as ultrasonic welding or thermowelding of thermoplastic components in the chassis material. A problem with the elastic laminate materials used for creating an elastic chassis structure is that they generally have poor weldability, resulting in weak side seams that will fail when putting on the article or when the article is being worn.
Accordingly, it is an object of the invention to provide an elastic pant-type absorbent article comprising elastic laminate materials and showing sufficient strength to withstand the forces arising when putting on and wearing the article.
It is also an object of the invention to offer an elastic pant-type absorbent article comprising elastic laminate materials and having openable side seams.
A further object of the invention is to provide a simple and efficient method for producing an elastic pant-type absorbent article having side seams showing sufficient strength to withstand the forces arising when putting on and wearing the article.